Error pops-up when laying footage from a sequence loaded in source monitor to a new sequence:
This is basically the same error as the one in this thread, but on the Mac side:
http://community.avid.com/forums/t/138008.aspx
Tried thrashing databases, new project, new user. Steps solve nothing.
Avid version 8.5.3
Macpro 5,1 2x2.66GHz 6-core, 38GB RAM MAC OSX El Capitan 10.11.3 with Nitris DX
Same problem on another same specced computer but with an AJA Io Express.
The same bug happened on 8.5.0 but it manifested itself as a Mainthread error and crashed Avid.